Supplemental restraint devices have become commonplace in vehicles in recent years and engineering and design efforts have increasingly focused on such devices deployable along vehicles' interior sides. In the event of a side impact or vehicle rollover event, a curtain or inflatable cushion is rapidly positioned between the vehicle passenger and the window/door of the vehicle. Due to the limited vehicle structure that separates an occupant from a rapidly moving body impacting the side of the vehicle, occupants may sustain much greater injuries in side-impact events than front or rear impacts. The energy absorbed by the vehicle structure tends to be substantially less than the energy which may be absorbed in front-end or rear-end collisions. Moreover, the forces generated in side-impact or vehicle rollover events may actually cause the occupant to be ejected from the side of the vehicle. Some vehicles, due to their structure as well as a possible increased rollover risk, present particular problems in this area.
Various mounting methods and restraint apparatus configurations have been developed to assist in protecting occupants during such events. One approach has been to position a deflated or folded restraint cushion or curtain behind a trim panel located along the vehicle roof rail. When deployment is desired, the deploying restraint is actuated to burst through or push aside the trim panel, ultimately being positioned adjacent the occupant, where it absorbs impact from the occupant's head and torso. Where inflatable cushions are used, however, the necessarily rapid rate of inflation, coupled with the consequences of an occupant's head striking the deployed cushion, presents a challenge to maintaining a side cushion in its optimum deployed position. As always, there are continual efforts to improve the stability of the deployed airbag.
In addition to the concerns of maintaining the cushion in an optimum position throughout an accident sequence, the impact of an occupant's body on the cushion may actually displace the cushion from a position of maximum effectiveness. In response to this problem and those discussed above, a variety of tethering and mounting schemes have been designed to better support the cushion during deployment. U.S. Pat. No. 6,237,938 to Boxey is exemplary. Boxey provides a vehicle occupant protection device tethered to a slidable element retained in a guide track. In Boxey, inflation of the protection device drives it away from the roof rail, between the occupant and vehicle window. As the device inflates, the slidable element is drawn along its track by the tether, apparently reducing movement of the bottom edge of the cushion in a direction perpendicular to the inflation direction. Boxey presents one known approach, however, it is limited in a number of ways. Most importantly, lateral support from the slide apparatus is limited by the inflation/deployment of the cushion. Only when inflation of the cushion has drawn the slider to the bottom of its track, which angles away from the cushion's deployment direction, is the cushion maximally supported. Further, tensioning of the cushion is limited by the cushion's inflation pressurization.